1. Field of the Invention
This invention relates to a process for producing acrylonitrile by a vapor-phase catalytic ammoxidation of propylene. More specifically, the invention relates to a process for producing acrylonitrile by the vapor-phase catalytic ammoxidation of propylene using a silica-supported multi-promoted iron/antimony oxide fluidized catalyst.
2. Description of the Prior Art
Since acrylonitrile is currently produced in very large quantities by the vapor-phase catalytic ammoxidation of propylene, even a slight increase in the yield of acrylonitrile results in a large economical advantage. Continuing efforts have therefore been made to develop catalysts having superior performance for the production of acrylonitrile. In view of recent concerns on environmental problems, development of catalysts which can be used to produce acrylonitrile in high yields with reduced amounts of byproducts, difficult to dispose of, has been strongly desired.
A large number of catalysts useful for the production of acrylonitrile by the vapor-phase catalytic ammoxidation of propylene are known, and many patents have been issued on these catalysts. However, only a few of them show superior results feasible for commercial operations.
An iron/antimony oxide mixed catalyst useful in the vapor-phase catalytic ammoxidation of propylene is disclosed in Japanese Patent Publication No. 19111/1963 (Japanese Pat. No. 420,264), U.S. Pat. No. 3,197,419, and British Pat. No. 983,755. Moreover, improved results are obtained by the addition of particular additives to such a catalyst, as disclosed in U.S. Pat. Nos. 3,338,952, 3,542,843, 3,591,620, 3,668,147, 3,716,496, and 3,988,359. These catalysts, however, are not entirely satisfactory from the standpoint of the yield of acrylonitrile and other properties when a fluidized bed catalytic reactor, which is advantageous in the commercial production of acrylonitrile, is used. In particular, the catalyst disclosed in U.S. Pat. No. 3,988,359 has many advantages, but the strength of this catalyst is not satisfactory for use in a fluidized bed.